This invention is directed to wooden pallets for material transport which are handled with fork lift trucks, and to their method of manufacture. More particularly, the invention is directed to pallets comprising deckboards nailed to vertically disposed notched stringers which are reinforced.
Pallets are used in ever-increasing number in commerce to transport virtually all types of merchandise. These pallets when loaded with merchandise almost by necessity are handled with fork lift trucks. When empty, however, they can be handled with fork lift trucks, but oftentimes are manually stacked or moved manually from one location to another. Pallets, therefore, while of simple design must meet numerous specifications, many of which are conflicting.
More specifically, pallets since they are a service item must be relatively inexpensive. To be inexpensive, they must be made of materials of relatively low cost and must be fabricated in a manner which will make most effective use of labor. Moreover, since the pallets are at times handled manually and since they are shipped from place to place with merchandise, they must be relatively light in weight in addition to having high structural strength. Most pallets, therefore, are made of wood and comprise vertical stringers with deckboards nailed thereto, top and bottom. For efficient construction the stringers are cut to the proper length. To facilitate handling with fork lift trucks, it is preferable to pick up the pallets on the side as opposed to an end of the pallet and, accordingly, the stringers are also notched for entrance of the fork of the fork lift truck. After cutting to proper length and notching, the stringers are fed to automatic stringer "feed boxes," with the deckboards then being applied and nailed with nail handguns or automatic nailers.
In spite of the acceptance of wood as the logical choice for pallet construction, pallets constructed from wood are subject to damage or breakage due to heavy loading and in being subjected to substantial mechanical impact from the fork end of the fork lift truck due at times to simple operator carelessness or indifference. Breakage in pallets with notched stringers occurs most often at the pallet end substantially immediately adjacent to the stringer notch. In order to reduce breakage and to increase the strength of wood pallets, various modifications to pallets have been suggested including incorporating metal braces between the stringers and deckboards; applying metal bands to the pallets at strategic points; reinforcing of the stringers by nailing; as well as constructing the pallets with bolts and/or metal pins extending through the stringer and deckboards. These efforts have been unacceptable to large users for various reasons. Metal braces and metal bands applied to the pallets not only increase material cost and at times make the pallets unacceptably heavy, but also increase labor costs during the course of construction and in large measure preclude the use of conventional automatic stringer feed boxes and nailing machines. Moreover, a pallet containing the metal braces and/or bands are difficult to repair once damaged since the conventional method of cutting the nails between the deckboards and stringers or otherwise conventional methods of pulling the nails connecting the deckboards and stringers cannot be conveniently employed. Nail reinforcement, while providing some improvement, has been limited by the lack of rigidity provided by reinforcement with relatively flexible nails driven into the stringers. Bolts and pins extending through the stringers and deckboards, while improving structural integrity, again greatly increase cost both from the standpoint of initial construction and repair. In the initial construction it is necessary to drill the deckboards and stringers in substantially perfect alignment and then insert the bolts. In order to avoid having boltheads or nuts interfere with the stacking of merchandise on the pallets and/or interfering with the setting down of the pallets and/or damaging merchandise when one loaded pallet is placed on another loaded pallet, the boltheads and nuts must be countersunk to provide a flush surface. This further increases the cost of the manufacturing operation and also requires the use of relatively thick deckboards for adequate strength. The countersinking of the boltheads into the deckboards also provides a weakened area at the point of countersinking, causing the deckboards to break at the weakened point.